From: julien.grall@linaro•org (Julien Grall)
To: linux-arm-kernel@lists•infradead.org
Subject: [Xen-devel] [PATCH v2 1/3] xen/arm: introduce XENFEAT_grant_map_11
Date: Tue, 08 Jul 2014 17:53:18 +0100 [thread overview]
Message-ID: <53BC21FE.2000705@linaro.org> (raw)
In-Reply-To: <1404835150.25940.9.camel@kazak.uk.xensource.com>
Hi Ian and Stefano,
On 07/08/2014 04:59 PM, Ian Campbell wrote:
> On Tue, 2014-07-08 at 16:54 +0100, Stefano Stabellini wrote:
>> On Tue, 8 Jul 2014, Ian Campbell wrote:
>>> On Tue, 2014-07-08 at 16:42 +0100, Stefano Stabellini wrote:
>>>> The flag tells us that the hypervisor maps a grant page to guest
>>>> physical address == machine address of the page in addition to the
>>>> normal grant mapping address. It is needed to properly issue cache
>>>> maintenance operation at the completion of a DMA operation involving a
>>>> foreign grant.
>>>>
>>>> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu•citrix.com>
>>>> ---
>>>> arch/arm/xen/enlighten.c | 6 ++++++
>>>> include/xen/interface/features.h | 3 +++
>>>> 2 files changed, 9 insertions(+)
>>>>
>>>> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
>>>> index b96723e..ee3135a 100644
>>>> --- a/arch/arm/xen/enlighten.c
>>>> +++ b/arch/arm/xen/enlighten.c
>>>> @@ -262,6 +262,12 @@ static int __init xen_guest_init(void)
>>>> xen_domain_type = XEN_HVM_DOMAIN;
>>>>
>>>> xen_setup_features();
>>>> +
>>>> + if (!xen_feature(XENFEAT_grant_map_11)) {
>>>> + pr_warn("Please upgrade your Xen.\n"
>>>> + "If your platform has any non-coherent DMA devices, they won't work properly.\n");
>>>> + }
>>>
>>> Unfortunately this isn't quite complete. On a system where all devices
>>> are behind an SMMU then we would want to be able to disable the 1:1
>>> workaround, which in turn would imply disabling this feature flag too
>>> (since it is no longer necessary and also impossible to implement in
>>> that case).
>>
>> That is true, but in such a system we would have to tell the kernel that
>> DMAing is safe, so this will turn into:
>
> Oh right, yes. Good then ;-)
FWIW, I've sent a patch series a couple ago to avoid using swiotlb when
the device is protected (see https://patches.linaro.org/25070/).
I should take time to rework properly and send a new version.
Regards,
--
Julien Grall
next prev parent reply other threads:[~2014-07-08 16:53 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-08 15:40 [PATCH v2 0/3] xen/arm: fix "xen_add_mach_to_phys_entry: cannot add" problem Stefano Stabellini
2014-07-08 15:42 ` [PATCH v2 1/3] xen/arm: introduce XENFEAT_grant_map_11 Stefano Stabellini
2014-07-08 15:49 ` Ian Campbell
2014-07-08 15:54 ` Stefano Stabellini
2014-07-08 15:59 ` Ian Campbell
2014-07-08 16:53 ` Julien Grall [this message]
2014-07-08 16:16 ` David Vrabel
2014-07-08 15:42 ` [PATCH v2 2/3] xen/arm: reimplement xen_dma_unmap_page & friends Stefano Stabellini
2014-07-08 15:42 ` [PATCH v2 3/3] xen/arm: remove mach_to_phys rbtree Stefano Stabellini
2014-07-08 16:05 ` [Xen-devel] [PATCH v2 0/3] xen/arm: fix "xen_add_mach_to_phys_entry: cannot add" problem Konrad Rzeszutek Wilk
2014-07-09 10:30 ` Stefano Stabellini
2014-07-09 13:47 ` Konrad Rzeszutek Wilk
2014-07-09 14:14 ` Stefano Stabellini
2014-07-09 14:31 ` Denis Schneider
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=53BC21FE.2000705@linaro.org \
--to=julien.grall@linaro$(echo .)org \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox